1. Field of the Invention
The invention relates to a fuel injection valve damping insulator that damps vibration produced in a fuel injection valve that injects fuel in an internal combustion engine.
2. Description of Related Art
Conventionally, in a so-called in-cylinder injection type internal combustion engine, that is a type of internal combustion engine in which fuel is injected into a combustion chamber, for example, a fuel injection valve is suspended between a cylinder head and a delivery pipe by having a portion toward a tip end of the fuel injection valve be inserted into and supported by an insertion hole of the cylinder head, and a portion toward the base end of the fuel injection valve be inserted into and supported by the delivery pipe (i.e., a fuel injection valve cup). Normally, in this kind of fuel injection valve, when fluctuations in the fuel pressure supplied via the delivery pipe occur due to the injection of fuel being started and stopped, vibration based on this fuel pressure fluctuation and operating vibration of the fuel injection valve occur. Therefore, a damping insulator that absorbs and suppresses vibration of the fuel injection valve is often installed between the fuel injection valve and the insertion hole of the cylinder head.
However, because the cylinder head and the delivery pipe are originally separate parts, the relative positions of these parts inevitably change due to tolerance related to machining and manufacturing of the parts, tolerance related to assembly during manufacture, and various vibrations and thermal deformation that occur with operation of the internal combustion engine, for example. That is, even with the fuel injection valve described above that is suspended between the cylinder head and the delivery pipe, the axis of the fuel injection valve becomes inclined with respect to the axis of the insertion hole of the cylinder head, and the fuel injection valve will become positionally offset at the position where it is supported by the cylinder head and the delivery pipe. This kind of positional offset may lead to a fuel leak by creating looseness in a portion of an O-ring that prevents fuel from leaking between the fuel injection valve and the delivery pipe (i.e., the fuel injection valve cup) or the like, at the base end side of the fuel injection valve.
Therefore, an insulator that aims to absorb and suppress vibration of a fuel injection valve, and reduce the effect from the axial inclination of the fuel injection has been proposed. The insulator described in Japanese Patent No. 4191734 is an example of one such insulator. The insulator described in Japanese Patent No. 4191734 includes an annular adjustment element 60 sandwiched between a shoulder portion 54 of a cylinder head 51 and a tapered stepped portion 57 of a fuel injection valve 55 that increases in diameter in a tapered shape so as to face the shoulder portion 54, as shown in FIG. 7. An injection nozzle 56 of the fuel injection valve 55 is arranged inserted through an insertion hole 52 (i.e., a receiving hole) of the cylinder head 51, and the shoulder portion 54 of the cylinder head 51 widens out to a side wall 53 of the insertion hole 52. The adjustment element 60 includes a first leg 61 that extends along the shoulder portion 54 of the insertion hole 52, and a second leg 62 that extends along the tapered stepped portion 57 of the fuel injection valve 55. The fuel injection valve 55 is configured to be elastically supported with respect to the cylinder head 51 by the first leg 61 surface-contacting the shoulder portion 54 of the insertion hole 52, and the second leg 62 surface-contacting the tapered stepped portion 57 of the fuel injection valve 55.
With this kind of insulator, during assembly, if an axis C2 of the fuel injection valve 55 becomes displaced between the insertion hole 52 of the cylinder head 51 and the delivery pipe, the first leg 61 will move along the shoulder portion 54 of the insertion hole 52 based on force generated by the second leg 62 that bends following the tapered stepped portion 57 of the fuel injection valve 55. As a result, the positional relationship of the fuel injection valve 55 with respect to the insertion hole 52 and the delivery pipe is able to be appropriately compensated for. However, when the internal combustion engine is operating, high pressure based on the fuel pressure described above is applied to the adjustment element 60 through the tapered stepped portion 57 of the fuel injection valve 55. At this time, the fuel injection valve 55 may no longer be able to elastically support the fuel injection valve 55 with respect to the cylinder head 51 due to metal fatigue from the fuel pressure accumulating in the adjustment element 60, or the adjustment element 60 plastic deforming as a result of the adjustment element 60 receiving unexpected pressure or the like. The position in the vertical direction of the fuel injection valve 55 that is no longer able to be elastically supported in this way with respect to the cylinder head 51 moves, so the fuel injection position will also change, and the like. As a result, an optimum combustion state may no longer be able to be maintained. Also, the adjustment element 60 that has lost is elasticity will transmit vibration produced by the fuel injection valve 55 based on the fuel pressure to the cylinder head 51 without damping it. As a result, noise due to the transmitted vibration may emanate from the internal combustion engine, and sensors of the internal combustion engine may erroneously detect the transmitted vibration as knocking, and the like.